class_name Currency
extends RefCounted
## Money. Everything is stored in COPPER — one integer, on GameState.purse_copper.
## The denominations exist so a bounded §6 move can name a unit (give_item(gold)
## is +10,000c); they are NOT stored buckets, so change-making never arises.
##
## The ratios are rules and live here in code. PRICES are content and live in
## /content (roadmap: "the economy is two systems"). Formatting happens only at
## the display edge — this is the one place that knows what "12g 40s 8c" means.

const COPPER := 1
const SILVER := 100
const GOLD := 10000

const VALUES := {"copper": COPPER, "silver": SILVER, "gold": GOLD}


static func is_currency(item_id: String) -> bool:
	return VALUES.has(item_id)


static func value(item_id: String) -> int:
	return int(VALUES.get(item_id, 0))


static func format(copper: int) -> String:
	# Empty denominations are suppressed and at least one unit always shows:
	# "0c", "47c", "1g 8c", "12g 40s". "0g 0s 8c" reads as a spreadsheet, not a
	# purse — and being broke should read as poverty (§3).
	if copper <= 0:
		return "0c"
	var parts: Array[String] = []
	var left := copper
	@warning_ignore("integer_division")  # denomination math — the remainder is carried, not lost
	var gold := left / GOLD
	if gold > 0:
		parts.append("%dg" % gold)
		left -= gold * GOLD
	@warning_ignore("integer_division")
	var silver := left / SILVER
	if silver > 0:
		parts.append("%ds" % silver)
		left -= silver * SILVER
	if left > 0:
		parts.append("%dc" % left)
	return " ".join(parts)